LARGE DOUBLE-STRANDED DNA VIRUSES WHICH CAUSE THE LYSIS OF A MARINE HETEROTROPHIC NANOFLAGELLATE (BODO SP) OCCUR IN NATURAL MARINE VIRAL COMMUNITIES

A virus (BV-PW1) which causes lysis of 2 strains of a marine heterotro phic nanoflagellate belonging to the genus Bodo (strains E1 and E4) wa s isolated from the coastal waters of Texas, USA. Transmission electro n microscopy of ultrathin sections of infected nanoflagellates reveale d the presence of intracellular virus-like particles 48 h following in fection, concomitant with a decline in flagellate numbers. The virus c ontains double-stranded DNA, is hexagonal in cross section, ca 230 to 300 nm in diameter and contains an electron dense core. It is morpholo gically similar to virus-like particles which have been observed in ot her heterotrophic nanoflagellates, and to viruses which have been isol ated which infect eukaryotic phytoplankton. Addition of the virus to c ultures of Pseudobodo parvulus (ATCC 50091, formerly Bodo parvulus) or Paraphysomonas imperforata (strain VS1) did not result in lysis. To o ur knowledge this is the first virus infecting heterotrophic nanoflage llates which has been isolated and maintained in culture. The presence of viruses in seawater which cause lysis of phagotrophic nanoflagella tes implies that viruses infect microzooplankton populations in the se a and suggests another important role for viruses in aquatic microbial communities.